[monochrome]

Do you have a source? I've always had the impression that screwdrive AF has always been extremely reliable.*

* Canon never used it.

I think @normhead means - because we never experienced AF failures in the screwdrive era, the SDM deal was doubly shocking relative to our elevated expections.

AFA 60-250 SDM, I understand the difference between the SDM motors and agree with normhead academically, but I’m just not going to take the risk without the ability to convert it. I’m not all that unhappy with the screwdrive on the 16-50 and 50-135, but I bought the used FA*80-200/2.8 instead of the 60-250.

I’ll probably go 100% FF anyway soon, letting go of all the DA lenses. The jury is out on whether I upgrade KP to K-new or just make the KP my backup camera.

[SSGGeezer]

I bought the used FA*80-200/2.8 instead of the 60-250.

What is your impression of it so far?

[luftfluss]

Exchange it for camel breath.

Eww, no thanks.

[normhead]

I think @normhead means - because we never experienced AF failures in the screwdrive era, the SDM deal was doubly shocking relative to our elevated expections.

AFA 60-250 SDM, I understand the difference between the SDM motors and agree with normhead academically, but I’m just not going to take the risk without the ability to convert it. I’m not all that unhappy with the screwdrive on the 16-50 and 50-135, but I bought the used FA*80-200/2.8 instead of the 60-250.

I’ll probably go 100% FF anyway soon, letting go of all the DA lenses. The jury is out on whether I upgrade KP to K-new or just make the KP my backup camera.

Understandable, once you been burned... I've read on other sites where a pro sold $25,000 worth of Canon gear to go Nikon, after a brand new $15,000 lens failed. It happens. At least you're still with Pentax. That probably makes you a loyalist.

---------- Post added 04-03-20 at 08:41 PM ----------

According to the SDM Reliability Survey Results the 60-250 is by far the most reliable of the old-school SDM zooms. Of course these are dated results, but I think the sample size is enough to draw meaningful conclusions.

If I can remember, the best failure rate was around 3% failures at lens rentals. Given that people with failures are more likely to vote, I'm not sure that's even out of line with industry standards.

For those who don't remember the trauma....
https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/130049-dar...aar-shoot.html

---

Last edited by normhead; 04-03-2020 at 05:51 PM.

[Wheatfield]

Eww, no thanks.

I will concede that your camel’s breath is better than my camel’s breath.

[monochrome]

What is your impression of it so far?

Better than the DFA100 and FA*200/8. Heavy, sharp, but 200mm is too long for my living room

[WorksAsIntended]

If I can remember, the best failure rate was around 3% failures at lens rentals. Given that people with failures are more likely to vote, I'm not sure that's even out of line with industry standards.

Those are completely uncomparable data.

The data from lens rentals are more or less complete data but for a more than average use case in terms of demand on the lenses. The amount of wear on rent items is generally higher than average privat use, this is true for almost every area. A photojournalist of course would be the opposite, he propably stresses his daily use lens even more.
The data from the poll are data without control. The majority of users does not state how the lense was used. In the end, there are probably a lot of people who just klicked a button because they feel one option should win, without owning the lens. If the people who had failure are more active in such a poll is up to debate, on the one hand people tend to talk about bad experiences a lot, on the other hand some might have left Pentax and are not in a Pentax related forum due to the failure. In any way, the data are completely flawed and can only be compared within the poll, not to the statistics by lens rentals. Those are data of different types.

[Rondec]

As the owner of two failed SDM DA* zooms that I’ve converted to screwdrive, “better” doesn’t move the needle for me.

I currently own two SDM lenses, neither of which has failed. The DA *16-50, which is now about 12 years old, I guess and the DA *55 which is 9 or 10 years old. Both seem to be working OK, but my DA *50-135 started getting flaky and I ended up selling it.

In the long run, Pentax needs to replace the SDM in the lenses with something else. They might be able to forego that with the 60-250 as the 70-210 is close enough, but the 16-50/50-135/55/300 all would warrant improvement in their lens drive systems and while they are at, they could tweak the optics on a couple of those, at least.

[normhead]

I currently own two SDM lenses, neither of which has failed. The DA *16-50, which is now about 12 years old, I guess and the DA *55 which is 9 or 10 years old. Both seem to be working OK, but my DA *50-135 started getting flaky and I ended up selling it.

In the long run, Pentax needs to replace the SDM in the lenses with something else. They might be able to forego that with the 60-250 as the 70-210 is close enough, but the 16-50/50-135/55/300 all would warrant improvement in their lens drive systems and while they are at, they could tweak the optics on a couple of those, at least.

They did swap in some new parts at some point... but as we all know, if you're buying second hand you won't know if you have the older set up that was more likely to fail.

---------- Post added 04-04-20 at 08:49 AM ----------

The data from the poll are data without control.

Believe me, this was debated ad nauseam at the time. Pentax's lack of communication made everything worse. Pentax's philosophy seems to be admit nothing, work quietly in the back ground on a fix. With problems the magnitudes of the DA*16-16 /DA*50-135 fiasco that was really poor strategy.

But in the end, a poor design or an issue blown out of proportion by the internet? Probably both were factors.

Pentax used to send equipment to Benjikan for testing. Having a 16-50 fail after they sent him back a defective lens probably hurt Pentax more than a multi-million ad campaign could fix. He was our poster boy.... even if you didn't experience a failure it made you wonder "If this is how they treat benjikan, how are they going to treat a nobody like myself.?" It was the last straw in Pentax's market share decline.

Salemen in stores bookmarked threads on their computers and showed customers why they shouldn't buy Pentax by pointing to the riot going on over here on the forum.

[SSGGeezer]

In the long run, Pentax needs to replace the SDM in the lenses with something else. They might be able to forego that with the 60-250 as the 70-210 is close enough, but the 16-50/50-135/55/300 all would warrant improvement in their lens drive systems and while they are at, they could tweak the optics on a couple of those, at least.

I can't argue the overall point but the new 55-300 PLM is nothing like the SDM lenses you seem to be grouping it with. I have heard of some focus issues on a few copies, but nothing about motor failure. My DA* 55 and DA* 50-135 have been reliable from when I bought them used here in the forums, while the 16-50s sample images never did anything that made me want to buy it. As the 16-50 seems to be the worst of the lot, I don't fell the need to be worried about failure since the 555 could be a manual lens, and the 50-135 can be converted and work well.

[Rondec]

I can't argue the overall point but the new 55-300 PLM is nothing like the SDM lenses you seem to be grouping it with. I have heard of some focus issues on a few copies, but nothing about motor failure. My DA* 55 and DA* 50-135 have been reliable from when I bought them used here in the forums, while the 16-50s sample images never did anything that made me want to buy it. As the 16-50 seems to be the worst of the lot, I don't fell the need to be worried about failure since the 555 could be a manual lens, and the 50-135 can be converted and work well.

The 55-300 isn't an SDM lens. I'm saying the old DA * SDM lenses need new motors, sooner rather than later. I just think they probably will forego working on 60-250 for awhile since they have the 70-210 in the line up now.

[SSGGeezer]

The 55-300 isn't an SDM lens. I'm saying the old DA * SDM lenses need new motors, sooner rather than later. I just think they probably will forego working on 60-250 for awhile since they have the 70-210 in the line up now.

Mis-read due to lack of coffee! Mea Culpa! My DA*300 has been perfect also but I haven't used it in quite a while, especially since I got my 150 450.

[Serkevan]

I can't argue the overall point but the new 55-300 PLM is nothing like the SDM lenses you seem to be grouping it with. I have heard of some focus issues on a few copies, but nothing about motor failure. My DA* 55 and DA* 50-135 have been reliable from when I bought them used here in the forums, while the 16-50s sample images never did anything that made me want to buy it. As the 16-50 seems to be the worst of the lot, I don't fell the need to be worried about failure since the 555 could be a manual lens, and the 50-135 can be converted and work well.

Maybe Rondec meant the DA 55 and DA 300 more than the 55-300?

EDIT: just saw your other post. Oops

[thibs]

Maybe Rondec meant the DA 55 and DA 300 more than the 55-300?

EDIT: just saw your other post. Oops

And add the DA*200 too btw.

[normhead]

SDM is weird. My DA*200 was at the point where I thought I'd have to send it in. Then it worked again....
My own suspicion is that the motors are underpowered. A little bit of grit, any friction in the AF movement, power loss from a cold or low battery can affect it. The funny thing on mine being when the DA*200 fails, the quick shift also fails so the lens becomes completely useless. IMHO the internal design of these lenses was just prone to failure. The testing of the implementation of SDM was driven by other companies adopting electric AF motors, not any particular expertise on the part of Pentax. Pentax could have done a lot better. And I'm sure that was in part driven by the need to have lenses that could function in either screw drive or with electric drive motors seriously complicating the design process.

KAF4 is definitely the future.